#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/wait.h>

#define NUM 1024
#define SIZE 64
#define SEP " "

char cwd[1024];
char enval[1024];
int lastcode = 0;

const char *getUsername()
{
    const char *name = getenv("USER");
    if (name)
        return name;
    else
        return "none";
}

const char *getHostname()
{
    const char *hostname = getenv("HOSTNAME");
    if (hostname)
        return hostname;
    else
        return "none";
}

const char *getCwd()
{
    const char *cwd = getenv("PWD");
    if (cwd)
        return cwd;
    else
        return "none";
}

int getUserCommand(char *command, int num)
{
    printf("[%s@%s %s]# ", getUsername(), getHostname(), getCwd());
    char *r = fgets(command, num, stdin);
    if (r == NULL)
        return -1;
    command[strlen(command) - 1] = '\0';
    return strlen(command);
}

void commandSplit(char *in, char *out[])
{
    int argc = 0;
    out[argc++] = strtok(in, SEP);
    while (out[argc++] = strtok(NULL, SEP))
        ;
}

int execute(char *argv[])
{
    pid_t id = fork();
    if (id < 0)
    {
        return -1;
    }
    else if (id == 0)
    {
        execvp(argv[0], argv);
        exit(1);
    }
    else
    {
        int status = 0;
        pid_t rid = waitpid(id, &status, 0);
        if (rid > 0)
        {
            lastcode = WEXITSTATUS(status);
        }
    }
    return 0;
}

void cd(const char *path)
{
    chdir(path);
    char tmp[1024];
    getcwd(tmp, sizeof(tmp));
    sprintf(cwd, "PWD=%s", tmp);
    putenv(cwd);
}

int doBuildin(char *argv[])
{
    if (strcmp(argv[0], "cd") == 0)
    {
        char *path = NULL;
        if (argv[1] == NULL)
            path = ".";
        else
            path = argv[1];
        cd(path);
        return 1;
    }
    else if (strcmp(argv[0], "export") == 0)
    {
        if (argv[1] == NULL)
            return 1;
        strcpy(enval, argv[1]);
        putenv(enval); // ???
        return 1;
    }
    else if (strcmp(argv[0], "echo") == 0)
    {
        char *val = argv[1] + 1;
        if (strcmp(val, "?") == 0)
        {
            printf("%d\n", lastcode);
            lastcode = 0;
        }
        else
        {
            printf("%s\n", getenv(val));
        }
        return 1;
    }
    else if (0)
    {
    }

    return 0;
}

int main()
{
    while (1)
    {
        char usercommand[NUM];
        char *argv[SIZE];
        // 1. 打印提示符&&获取用户命令字符串获取成功
        int n = getUserCommand(usercommand, sizeof(usercommand));
        if (n <= 0)
            continue;
        // 2. 分割字符串
        // "ls -a -l" -> "ls" "-a" "-l"
        commandSplit(usercommand, argv);
        // 3. check build-in command
        n = doBuildin(argv);
        if (n)
            continue;
        // 4. 执行对应的命令
        execute(argv);
    }
}